Polyetherimide ester polymers comprised of the reaction products of (a) a low molecular weight diol, (b) a dicarboxylic acid, and (c) a high molecular weight polyoxyalkylene diimide diacid are known and are described in U.S. Pat. Nos. 4,544,734; 4,556,705 and 4,556,688. These poly(etherimide ester) elastomers exhibit excellent stress-strain properties, low tensile set, high melting temperatures and/or excellent strength/toughness characteristics as well as high flexibility, which render them especially suitable for molding and extrusion applications. In the preparation of these elastomers the amounts of polyoxyalkylene diimide diacid and dicarboxylic acid reactants employed are such that the weight ratio of the polyoxyalkylene diimide diacid to dicarboxylic acid is from about 0.25 to about 2.0:1.
It has now been discovered that polyetherimide ester polymers can be provided which exhibit higher flexural modulus and, therefore, better stiffness than these conventional polyetherimide esters. The polymers of the instant invention are obtained by utilizing relatively low weight ratios of the diimide diacid to the dicarboxylic acid reactants.